Yep, profit is probably the main reason.
I played a CVP-609 several weeks ago...beautiful...excellent speaker system, and very attractive cabinet. Absolutely lovely action, if you are fond of 88 weighted graded hammer.
The owner was very pleased with it, indeed, and well he should be, considering it's price. Similar styles and features as the Tyros4 but without the latter's 250 Gig HD.
Another thing that cripples the DGX is that the accompaniment is still only two variations...basically the style engine out of the lower end PSR.
And yes, a P-105 with the guts of an S750 would be a nice combination.
Ian
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Yamaha Tyros4, Yamaha MS-60S Powered Monitors(2), Yamaha CS-01, Yamaha TQ-5, Yamaha PSR-S775.